After three long weeks, we're seeing what may be the first big break in that missing passenger jet. Hundreds of miles in a whole direction. ABC's David Wright on the new lead. Reporter: Could this be a piece of floating debris from flight 370? It was spotted by two separate planes. This, in a vast stretch of ocean they just started searching today. Ten planes went out in the new search area. This New Zealand plane was the first to find anything significant. By the end of the day, half the search planes, 5 out of 10 came back with reports of debris. The most promising day yet. A day that began almost at square one, the authorities abruptly moving the focus 680 miles northeast. Far away from the satellite images they had been chasing for days. Effectively the search to date has been a waste of time, given it's focused on that southwest area? I don't count the original work as a waste of time. Reporter: The new focus -- an area the size of Virginia. Why the change? Boeing, rolls Royce U.S. And UK investigators re-analyzed military radar Readings and concluded flight 370 was flying faster than previously thought, burning through fuel more quickly and they concluded, when that fuel ran out, the plane plummeted into the ocean far north of the earlier estimates. One piece of data, one new analysis can change things greatly. Here, by a thousand miles of where the aircraft may have come down. Reporter: Officials are now more optimistic than ever they're finally on the right track to get chances. A few hours from now, China's largest rescue ship already if the search area is expected to pick up the debris and determine conclusively if it's from flight 370. This new search area is cold and remote. The weather is better. Better visibility for the planes. The seas less choppy. If they have found the debris field, they may be able to move much more quickly now.

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'This Week': Search for Malaysia Air 370

ABC News' David Wright and Cmdr. William Marks of the U.S. 7th Fleet on the race to find Malaysia Air 370.

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